1. Field of the Invention
The present invention relates to a cooling system for a battery pack including a plurality of battery cells.
2. Description of Related Art
Japan Patent Publication Number 2001-57196 discloses a battery pack 1 shown in FIG. 6. The battery pack 1 includes a plurality of battery cells 2 connected electrically in series. The plurality of cells 2 are bound together mechanically in parallel and integrated by a band 4 connecting end plates 3 provided at outermost battery cells 2, as shown.
Numeral references 5 and 6 in FIG. 6 indicate connecting modules (also called as bus-bar modules or battery connecting plates). The connecting modules 5 and 6 include connecting clamps (bus bar) to connect electrodes 7 of the adjacent cells 2, and are formed by insert molding the connecting clamps in a resin holder. The connecting module 5 also includes a battery-voltage-detecting terminal, while the connecting module 6 only includes the connecting clamps. A lead wire is connected to the battery-voltage-detecting terminal and to a battery-voltage-detecting unit 8. Electric wires connected to each of positive and negative electrodes of the battery pack 1 are not shown.
Another example of the connecting module (bus-bar module, battery connecting plate, etc.) is disclosed in Japanese Patent Publication Number 2004-31049 by the applicant of the present application.
The battery pack supplies electric power to an electric motor of, for example, an electric-motor vehicle or a hybrid-electric-motor vehicle. Recently, lithium-ion secondary batteries are used for the battery pack. It is known that in use, the battery pack generates extreme heat, for example at the time of large current discharge. In order to cool the battery pack, a cooling system as disclosed in Japan Patent Publication Number 2006-210245 is known.
The cooling system disclosed in Japan Patent Publication Number 2006-210245 includes a heat pipe having a heat absorbing member, a heat dissipating member, a fin and a flat-plate (portion). This heat pipe is arranged integrally with the battery pack for cooling the battery pack.
For the cooling system of the prior art, a separate unit which is dedicated for cooling, i.e. the above-described heat pipe, is employed. This leads to an increase in manufacturing cost and also an increase in a number of components required for the battery pack. Furthermore, since the heat pipe includes the heat absorbing member, the heat dissipating member, the fin and the flat-plate, the heat pipe itself includes a number of components, thereby requires many steps in manufacturing. Furthermore, an installation space for the heat pipe must be taken into account.